1. Field of the Invention
The present invention relates to a surface mounting electronic component which is mounted on a surface of a printed circuit board or other suitable substrate, and a method of manufacturing the component. More specifically, the present invention relates to a surface mounting electronic component having external electrodes including plated coatings disposed on metallic coatings and a method for manufacturing such a component.
2. Description of the Related Art
Conventionally, various surface mounting electronic components have been proposed in order to realize smaller electronic apparatuses.
FIG. 14 is a perspective view illustrating an example of a conventional surface mounting electronic component.
In an electronic component 121, external electrodes 123-125 are disposed on the outer surfaces of an electronic component body 122. The external electrodes 123-125 have a laminated structure of metallic coatings with excellent electroconductivity and plated coatings located on the metallic coatings.
The above-described metallic coatings are composed of a metal with excellent electroconductivity such as Ag to ensure electrical connection with the electrodes (not shown in the drawing) located inside of the electronic component body 122. On the other hand, the plated coatings laminated on the metallic coatings are composed of Sn, an Snxe2x80x94Pb alloy, or such material having excellent soldering properties.
Various configurations have been conventionally proposed for such external electrodes in the above-described surface mounting electronic component. For example, in the surface mounting electronic component described in Japanese Unexamined Patent Application Publication No. 3-258107, a plurality of external electrodes are arranged to wrap around the top surface, a pair of side surfaces and the bottom surface of an electronic component body. Similar surface mounting electronic components are disclosed in Japanese Unexamined Utility Model Application Publication Nos. 3-117933 and 4-75425.
However, in the representative conventional surface mounting electronic component 121 shown in FIG. 14, differences occur between the thicknesses of the above-described plated coatings in the external electrodes 123 and 125 disposed on the ends in the lengthwise direction and the thickness of the plated coating disposed in the external electrode 124 located in the center thereof. More specifically, the thicknesses of the plated coatings in the external electrodes 123 and 125 disposed on the ends in the lengthwise direction are larger than that of the plated coating in the external electrode 124 located in the center.
The above-described plated coatings are formed by wet type barrel plating. As shown in FIG. 15, metallic balls 126 as an electroconductive medium are contacted with metallic coatings 123A-125A to perform plating in the course of wet type barrel plating, wherein the metallic balls 126 are contacted with the metallic coatings 123A and 125A located on the ends in the lengthwise direction for a longer time than with the central metallic coating 124A. At the end of the plating process, this inevitably causes the thicknesses of the external electrodes 123 and 125 on the ends in the lengthwise direction to be larger than that of the external electrode 124 in the center as shown schematically in the lower portion of FIG. 15.
With such differences in the thickness of the plated coatings as shown above, the electronic components 121 stick to each other in the course of barrel plating, resulting in defective products. There are also problems such as increased variation in the configuration of the electronic components 121 finally obtained and increased cost caused by excessive consumption of materials required for plating.
In order to overcome the problems described above, preferred embodiments of the present invention provide a surface mounting electronic component with a plurality of external electrodes disposed on the outer surfaces of the electronic component constituting member, and each of the external electrodes having a structure in which plated coatings are laminated on metallic coatings by wet type barrel plating, wherein a plurality of external electrodes have very slight variations in thicknesses of the plated coatings. Thus, it is possible to reduce the frequency of defective components in the course of production, there are only slight variations in the appearance of the electronic components thus obtained, and materials for plating can be utilized efficiently, making it possible to reduce costs, and to provide a novel and advantageous method for producing the component.
According to a preferred embodiment of the present invention, a surface mounting electronic component includes an electronic component constituting member having a top surface, a bottom surface, a pair of side surfaces and a pair of end surfaces, and a plurality of external electrodes disposed on the outer surfaces of the electronic component constituting member and including metallic coatings and plated coatings disposed on the metallic coatings by a wet type plating method, the plurality of external electrodes are arranged at least on the bottom surface of the electronic component constituting member, and extend to reach the edges located between the bottom surface and the side surfaces, external electrodes located in the vicinities of the above-described end surfaces are located apart from each of the edges disposed between the end surfaces and the top surface, the bottom surface or the side surfaces, each external electrode has approximately the same area, and the total of the electrode lengths of sections of each external electrode is approximately the same, in which the sections are located on each of the edges disposed between the side surfaces and the upper or bottom surface of the electronic component constituting member.
According to another preferred embodiment of the present invention, a surface mounting electronic component including an electronic component constituting member having a top surface, a bottom surface, a pair of side surfaces and a pair of end surfaces, and n (where n is a natural number) external electrodes disposed on the outer surfaces of the electronic component constituting member and including metallic coatings and plated coatings disposed on the metallic coatings by a wet type plating method, each of the external electrodes is disposed at least on the bottom surface of the electronic component constituting member, and extends to reach the edges located between the bottom surface and the side surfaces, and n (where n is a natural number) of the external electrodes are aligned in the lengthwise direction, the lengthwise direction being determined along the line made by connecting a pair of end surfaces, each of the areas of the external electrodes is represented by S1xe2x88x92Sn with the relationships of S1 less than S2≈S3 . . . ≈Snxe2x88x921 and Sn less than S2≈S3 . . . ≈Snxe2x88x921; and the total of the electrode lengths of sections of each external electrode is represented by L1xe2x88x92Ln, with the relationships of L1 greater than L2≈L3 . . . ≈Lnxe2x88x921 and Ln greater than L2≈L3 . . . ≈Lnxe2x88x921, in which the sections are located on each of the edges disposed between the side surfaces and the upper or bottom surface of the electronic component constituting member.
In a surface mounting electronic component according to the first and second preferred embodiments of the present invention (hereinafter referred to as xe2x80x9cthe present inventionxe2x80x9d), there are preferably notches formed on the external electrodes at the ends in the lengthwise direction of the electronic component constituting member. In a more specific preferred embodiment, the above-described notches are arranged to open toward the above-described end surfaces on the top surface of the electronic component constituting member.
Also, in a surface mounting electronic component according to various preferred embodiments of the present invention, the above-described electronic component constituting member may be an electronic component body, or a packaging member on which an electronic component element is to be mounted or in which it is to be stored. When the electronic component constituting member is a packaging member, an electronic component element is further mounted on or stored in the above-described packaging member.
According to another preferred embodiment of the present invention, a method for manufacturing a surface mounting electronic component includes the steps of forming metallic coatings for a plurality of external electrodes on the outer surfaces of an electronic component constituting member having a top surface, a bottom surface, a pair of side surfaces and a pair of end surfaces, and forming a plurality of external electrodes by forming plated coatings according to a wet type barrel plating method on the metallic coatings by putting metallic balls and the electronic component constituting member into a barrel pot, wherein, the plurality of metallic coatings are formed at least on the bottom surface of the electronic component constituting member, and extend to reach the edges disposed between the bottom surface and the side surfaces, metallic coatings formed in the vicinities of the end surfaces are located apart from each of the edges formed between the end surfaces and the top surface, the bottom surface or the side surfaces, and each metallic coating has approximately the same area, and the total of the lengths of sections of each metallic coating is approximately the same, in which the sections are located on the edges of the electronic component constituting member.
According to yet another preferred embodiment of the present invention, a method of manufacturing a surface mounting electronic component includes the steps of forming metallic coatings for a plurality of external electrodes on the outer surfaces of an electronic component constituting member having a top surface, a bottom surface, a pair of side surfaces and a pair of end surfaces, and forming a plurality of external electrodes by forming plated coatings according to a wet type barrel plating method on the metallic coatings by putting metallic balls and the electronic component constituting member into a barrel pot, wherein n (where n is a natural number) metallic coatings are aligned in the lengthwise direction, the lengthwise direction being determined along the line made by connecting a pair of end surfaces of the electronic component constituting member, each of the areas of the metallic coatings is represented by S1xe2x88x92Sn, with the relationships of S1 less than S2≈S3 . . . ≈Snxe2x88x921 and Sn less than S2≈S3 . . . ≈Snxe2x88x921; and the total of the electrode lengths of sections of each external electrode is represented by L1xe2x88x92Ln with the relationships of L1 greater than L2≈L3 . . . ≈Lnxe2x88x921 and Ln greater than L2≈L3 . . . ≈Lnxe2x88x921, in which the sections are located on the edges of the electronic component constituting member.
In the methods for manufacturing a surface mounting electronic component according to the third and fourth preferred embodiments of the present invention, notches are formed preferably on the metallic coatings located on both ends in the lengthwise direction. In a more specific preferred embodiment, the notches are arranged to open toward the end surfaces on the top surface of the electronic component constituting member.
Also, in the methods according to the third and fourth preferred embodiments of the present invention, the above-described electronic component constituting member may be an electronic component body or a packaging member on which an electronic component element is to be mounted or in which it is to be stored.